ARCTIC

Arctic Research Consortium of the United States Member Institution Spring/Autumn 1999

Arctic Research at Lamont-Doherty Earth Observatory

Early Years of Lamont Research in the High Arctic olumbia University’s Lamont- CDoherty Earth Observatory (LDEO) entered the arena of arctic research more than four decades ago, when the Alaskan Air Command established Drifting Station A (or Alpha) on a 3 m-thick ice floe at 83° N 165° W. Station A was a U.S. con- tribution to the International Geophysical Year in 1957. Lamont scientists under the general direction of Jack Oliver and field leader- ship of Ken Hunkins conducted a pro- gram of geophysical and oceanographic research at the station, while investigators from other institutions carried out pro- grams of upper atmosphere, meteorologi- Lamont researchers have reconstructed annual temperatures for the arctic zone (65–90°N) during the past 400 years cal, sea-ice, and biological research. The using tree-ring width data from 12 sites near circumpolar treeline and three sites at northern, elevational treeline. Ten Lamont program used many instruments or more trees were sampled at each site. At all the sites, annual growth is limited by temperature. The regression used and techniques that had been developed principal component analysis to reduce the number of predictors and one forward lag of the series to account for carryover effects of temperature on tree growth. The regression explains 66% of the variance in temperature after adjustment for by Doc Ewing and other Lamont scientists degrees of freedom lost due to the regression. The tree-ring reconstruction helps quantify the unusual warming that is for exploration of the open oceans, modi- reflected in other arctic investigations. This and similar reconstructions provide a long-term context for interpreting fied for use from the ice camp. Important present changes in arctic regions (figure by Gordon Jacoby). results included the following: • echo soundings mapped the Alpha Rise • the first seismic refraction lines in the • a new understanding of wind-driven and Canada Abyssal Plain; Arctic Ocean led to understanding of motion of the ice pack was obtained. • measurements of currents yielded the upper crustal structure in the region; Other ice camps, most led by Ken the first direct observations of the • the first bottom photographs ever taken Hunkins, followed: Ekman spiral, which had been predicted in this ocean showed the life and ice- • Drifting Station Charlie led by George 50 years earlier; rafted rocks on the ocean floor; and Cvijanovich; • Fletchers Ice Island (T-3) from 1962– amont-Doherty Earth Observatory conducts a wide range of research in the 1974; LArctic and high-latitude regions of the northern hemisphere. These studies began • the Arctic Ice Dynamics Joint Experi- in 1957 with support from the U.S. Air Force Cambridge Research Center and, ment (AIDJEX) ice camps in the 1970s; soon thereafter, the Office of Naval Research (ONR). Support for recent and current • the Fram Expeditions in 1979. research is provided by ONR, the National Aeronautics and Space Administration The first Arctic Ocean precision depth (NASA), the National Oceanic and Atmospheric Administration (NOAA), the recorder and nuclear magnetic resonance Department of Energy (DOE), National Geographic, Palisades Geophysical Institute, magnetometer measurements were made the Geological Survey of Canada, and the NSF Office of Polar Programs, Ocean from Drifting Station Charlie. New Sciences program, Climate Dynamics program, and Earth System History program. instruments, such as the first satellite (continued on next page) 1 navigator—which was a classified system Research on Kodiak Island led to the Oceanic Uptake of Carbon Dioxide (CO2) at the time—and a seismic sparker, led to discovery of the “Fern Gap”, a Younger Since 1983, Lamont’s Ocean CO2 extensive mapping of Arctic Ocean Dryas equivalent, pointing to the dramatic Group, headed by Taro Takahashi, has bathymetry and sediment layers from T-3. role of this abrupt climate change in the been collaborating with Jon Olafsson Simultaneous profiling of temperature, North Pacific. (Marine Research Institute, Reykjavik, salinity, and currents at an array of four More recent research on the paleo- Iceland) for field studies aimed at under- AIDJEX camps revealed 127 separate sub- ecology of the Mesa Site, on the North standing seasonal and interannual changes surface anticyclonic eddies at depths of 50- Slope of Alaska, shows that peat formation in CO2 and nutrient chemistry and in 300 m. These eddies were approximately signals major environmental change in CO2 uptake in waters of the Irminger, 10 km in diameter and covered nearly the Arctic. Peteet, in collaboration with Iceland, and Norwegian seas. 25% of the Beaufort Sea. Helicopter sur- A. Andreev (Institute of Geography, In 1993–1995, researchers observed veys conducted from the Fram Expedition Moscow), has also led peatland research that the concentrations of CO2 and nutri- ice camps revealed anomalous diurnal tidal in Siberia and published results from the ents were drawn down by phytoplankton currents over the Yermak Plateau. The ice- Pur-Taz region of western Siberia. In col- blooms in mid-April through July. Con- camp studies were followed by the Mar- laboration with GISS modelers Anthony centrations of silicate, nitrate, and phos- ginal Ice Zone Experiment in 1983–84 Del Genio and Ken Lo, Peteet is continu- phate in surface water dropped from high and the Cooperative East Arctic Research ing sensitivity tests of climatic forcing winter values to nearly zero. Total CO2 Expedition in 1988–89, which gave new based on the paleoenvironmental results concentration was also drawn down at the results on the behavior of oceanographic from the Arctic and sub-Arctic. end of blooms. As a result, the partial pres- exchange through Fram Strait. Ice cores contain detailed records of sure of CO2 (pCO2) in surface water also paleoclimate, including large and abrupt dropped from 3% under-saturation in Paleoclimate Studies—Tree Rings changes in atmospheric dust. Dust found winter to approximately 24% under-satu- Gordon Jacoby and Rosanne D’Arrigo in polar ice cores can vary in amount by ration at the height of blooms. of the Tree-Ring Laboratory at Lamont more than two orders of magnitude. Pierre Thus, the oceans near and north of have been collecting samples at northern Biscaye and Francis Grousset are investi- Iceland become strong CO2 sinks during treeline (70°30' N) for more than two gating the continental origins of the dust spring through summer months. The decades. In 1989, the first reconstructions as indicators of past atmospheric change. strong drawdown of surface water pCO2 of large-scale temperature were published. Their approach has been to measure is one of the major processes causing the Since then, Lamont scientists and others characteristics of the dust that may high-latitude North Atlantic and its adja- have incorporated these data in many identify source areas. The tracers are: cent seas to be a major sink of CO2 in the reconstructions of northern hemisphere • clay mineralogy, which is dependent on global oceans. To document interannual and arctic temperature history. Ongoing the climate; and changes, the field study is continuing in studies in Alaska and the Taimyr Penin- • Sr-, Nd-, and lead-isotope composition, collaboration with research groups in Ice- sula, Siberia are producing new data for which are related to the rock type and land and other Nordic countries. improved reconstructions and information geologic age of the rocks from which about climatic and ecological changes in the local sediments in the source area Heat Flux and Ice Studies the Arctic. The Siberian studies, coordi- were derived. With the Surface Heat Budget of the nated with Russian scientists, are produc- In collaboration with Danish colleague Arctic (SHEBA) project (see Witness, this ing millennial-length records by using Anders Svensson, Biscaye and Grousset issue), Lamont has continued its long living, relict, and subfossil samples from have applied this approach to dust from tradition of ice-camp work in the Arctic. the northernmost trees on the planet. the two ice cores retrieved from the Doug Martinson is a co-principal investi- Greenland summit (see Witness Spring gator in the upper ocean physical oceanog- Paleoecology 1997), which hold records of the past raphy component of SHEBA. Martinson, The Paleoecology Lab at LDEO has a 110,000 years. The deserts of Eastern Asia Miles McPhee (McPhee Research), Tim history of research on Quaternary climate are the source of the Summit dust. The Stanton (Naval Postgraduate School), and and vegetation history along the southern researchers propose that if the source area Jamie Morison (University of Washing- coastline of Alaska. Projects led by of the dust has not changed significantly ton) are investigating the detailed hydro- Dorothy Peteet, also at NASA’s Goddard in size or location despite severe changes graphic structure of the upper 150 m of Institute for Space Studies (GISS), have in global climate and dust flux, then varia- the Arctic Ocean and how it evolves sea- used high-resolution pollen, macrofossil, tions in the amount of dust found in the sonally from continuous CTD profiles. and radiocarbon dating of lake and peat- cores must be the result of changes in the Some of the early findings include: land sediments. Peteet has focused particu- intensity of winds in the source area. • unusually fresh surface water, and lar attention on migration rates of spruce, Dust extracted from snow deposited over • unusually thin ice compared to data western hemlock, and mountain hemlock the past decade also seems to have been collected during the AIDJEX project along the south-central Alaskan coastline derived primarily from Eastern Asia. To in the 1970s. from Yakutat to Kodiak Island. further pin down the provenance of the Jay Ardai served as chief scientist of Recent proposals have centered on the dust and its degree of change, the research- the SHEBA ice camp during some of the Bering-Steller Glacier region, where new ers are continuing to analyze source-area winter months; Jay had also played an results point to advances and retreats of samples from as many northern hemi- integral role in the work of many previous this glacier throughout the Holocene. sphere locations as possible. ice camps, beginning with T-3. 2 Most recently, Martinson and Mike Steele (University of Washington) have employed in the Arctic techniques that were developed in the Antarctic for esti- mating ocean-ice heat fluxes. Steele and Tim Boyd (Oregon State University) documented the loss of the near-surface cold halocline layer (CHL) in the 1990s— a significant change in the upper ocean of the eastern Arctic. Martinson and Steele have shown that, without the CHL, the arctic water column looks and behaves like the Antarctic water column, with signifi- cant winter ocean heat fluxes (15–20 watts/m2) and reduction of winter ice growth by 70–80% relative to previous years when the CHL was present. If the CHL absence continues with no compen- sating changes in atmospheric forcing or ice advection, the long-term stability of the perennial ice pack will be in question.

Freshwater Sources and Circulation The Arctic receives approximately 10% USS Pogy, surfaced in the Arctic Ocean, enabling a hydrocast from the adjacent ice during the SCICEX ’96 expedition. of the total global river runoff. Freshwater Lamont principal investigators have been extensively involved in the multidisciplinary scientific projects carried out on these cruises. The late Marc Langseth chaired the scientific steering committee for the first cruise in 1993, and Jay is also supplied by sea-ice meltwater and Ardai, Dale Chayes, Bernie Coakley, and Ray Sambrotto have sailed on the two-month long submarine voyages (photo by the relatively fresh Pacific Water by Ray Sambrotto). (Bering Strait) inflow. Export of these large volumes of freshwater through Fram Water Mass Formation and Circulation More recent studies by Schlosser, Strait and the Canadian Archipelago may Bill Smethie and Peter Schlosser have Boenisch, Doug Wallace (University of influence deep water formation in the been measuring a variety of trace sub- Kiel), and John Bullister (NOAA/PMEL) Greenland and Labrador seas, which may stances in the Greenland-Iceland-Norwe- have revealed that renewal of the bottom in turn affect global climate. gian (GIN) seas since the early 1980s and water by deep convection ceased in the Peter Schlosser, Brenda Ekwurzel, and have participated in numerous icebreaker early 1980s, with the deep water evolving Gerhard Boenisch use the distribution of expeditions to the Arctic Ocean (Polar- toward deep Arctic Ocean characteristics. mass, salt, oxygen isotopes, and nutrients stern, Louis St. Laurent, Oden, Polar Sea, Ocean studies by Smethie and Schlosser • to determine sources of freshwater; and Polar Star) from the mid-1980s to the have shown that: • to estimate the respective proportions of present. In collaboration with European • the upper mixed layer beneath the ice the total volume in the surface waters of colleagues (Reinhold Bayer, Markus cover is renewed on a time scale of 5–10 3 3 the Arctic Ocean. Frank, Hugo Loosli, and Bernd Kromer), years, based on H/ He measurements; Their goal is to understand the vulner- Smethie obtained chlorofluorocarbon • the flow pathways of the two branches ability of Arctic Ocean circulation to (CFC) measurements, and Schlosser (Fram Strait and Barents Sea) of Atlan- changes in the freshwater budget. Com- obtained 3H/3He, 14C, and 39Ar tic-derived intermediate water are clearly 3 3 parison of 18O data collected in the Eur- measurements from much of the Eurasian seen in the H/ He and CFC data. Both asian Basin in 1991 and 1996 indicates Basin and parts of the Makarov and Cana- branches follow the bathymetry in a cy- a shift in river-water transport from the dian basins. In 1993, both investigators clonic flow pattern that extends along Eurasian Basin to the Canadian Arctic. collected data from the first Scientific Ice the Lomonosov Ridge and across the Large-scale general circulation models Expedition (SCICEX) submarine cruise ridge into the Canadian Basin, reaching for the Arctic Basin are being used by (see Witness Spring 1996), and they con- the central and southern Canadian Schlosser and Bob Newton in collabora- tinue to participate in these annual cruises Basin in 15–20 years; and tion with Wieslaw Maslowski (Naval Post- under the heavily ice-covered central • the deep and bottom water renewal 14 39 graduate School) to further understand Arctic Ocean (see Witness, this issue). times, based on C and Ar data, the freshwater balance in the Arctic The early 1980s GIN seas studies are approximately 450 years for the Ocean. These models are forced with showed that: Canadian Basin and 200 years for the ECMWF re-analysis winds for the • deep convection renewed the deep the Eurasian Basin. 1979–1993 time period and are fit to the Greenland Sea on a time scale of temperature, salinity, and 18O observa- approximately 30 years; and Arctic Contaminants tions. The redistribution of fresh water • the exchange rate of water between the Stephanie Pfirman, Peter Schlosser, indicated by the 18O data has been deep GIN seas and the deep Arctic was Bob Newton, Bill Smethie, and Bob simulated by the model. about 1 Sv (106 m3s-1). Anderson are investigating potential 3 pathways of contaminants in the Arctic amount of carbon entering the halocline High-Latitude Mantle Studies in collaboration with Roger Colony and from the various sources, based on Lavas that erupt at ocean-ridge spread- Hajo Eicken (University of Alaska alkalinity and other tracers for river water. ing axes are windows into the composition Fairbanks), Ignatius Rigor (University Chris Langdon has been measuring of the shallow mantle. Iceland is the of Washington), and Wieslaw Maslowski oxygen concentrations from underway largest mid-ocean ridge mantle plume. (Naval Postgraduate School). sensors on the SCICEX cruises as well as Steve Goldstein and German colleagues Modeling and field programs have on-board Winkler titrations. Variations in K. Haase (University of Kiel) and investigated the origin and fate of drifting oxygen are useful in sorting out the impor- C. Devey (University of Bremen) are con- multiyear sea ice and its role in transport- tance of locally produced vs. advected car- ducting a petrological and geochemical ing contaminants across the Arctic Basin. bon respiration. Such distinctions are criti- study on the Kolbeinsey spreading ridge The researchers are reconstructing the age, cal for understanding the Arctic’s role in north of Iceland (69°–72° N) to investi- origin, and trajectory of sea ice based on the carbon cycle and how this may change gate relationships between mantle flow, tracer analysis of cores from the ice and with a reduction of ice cover. mixing processes, and magmatic processes comparison with predicted backward forming the oceanic crust near a mantle trajectories. Research on the potential Marine Geology and Geophysics plume. The spreading ridges near Iceland for transport of contaminants by ocean Since 1995, the U.S. Navy has pro- represent extremes in the global variations currents includes modeling and tracer vided a Sturgeon Class fast attack subma- of water depth, crustal thickness, and geochemistry (85Kr, CFCs, 3H/3He, rine for an annual unclassified SCICEX major element compositions. Recently d18O) to investigate likely pathways and cruise in the Arctic Ocean (see Witness, erupted glass has been sampled at a spatial residence times. this issue). The quiet, stable submarine resolution of 2–4 km, the highest for any Both sea-ice trajectories and surface provides an ideal platform for the efficient mid-ocean ridge segment. and near-surface currents show marked acquisition of underway geophysical data. The study will generate a comprehen- interannual variations forced by changes James Cochran and Bernard Coakley have sive set of major trace element and isotopic in the atmospheric circulation, which will used SCICEX geophysical data to investi- data (Sr, Nd, Pb, He). While chemical impact the fate of entrained contaminants. gate the structure of the Gakkel Ridge— variations are affected by the melting and For example, observations and modeling the slowest-spreading section of the global cooling of magma/rock, isotope ratios are (in collaboration with Maslowski) show mid-ocean ridge system (at 0.6–1.3 cm/yr). not; they “see through” these processes that fresh water and any dissolved Analyses of SCICEX gravity and bathy- and trace the spatial distribution of the agricultural or industrial contaminants metry profiles across the Gakkel Ridge source rocks that melt to form the mag- discharged by rivers have recently been clearly show that: mas. The combination of chemical and taking a more easterly path than they did • the crustal thickness on the ridge must isotopic data for samples collected with before the late 1980s. be less than 3 km; and such a high spatial resolution will make • extensive areas with no crust, or very this the most comprehensive regional Marine Biology thin crust, may exist. geochemical data set available for a ridge Raymond Sambrotto has been working This result places important constraints on segment, and it will be a unique resource to clarify the sources and sinks of carbon models of melt production and migration for geophysical and geochemical modeling in the western Arctic. Sampling for the at mid-ocean ridges. Dale Chayes, in col- of melting and mantle flow. inorganic and organic carbon pools was laboration with Margo Edwards (Univer- conducted along the Arctic Ocean Section sity of Hawaii), has led the effort to create in 1994 and on SCICEX submarine a unique set of active sonar instruments cruises. The goals are: for SCICEX missions. The Seafloor Char- • to better define the size of the various acterization and Mapping Pods (SCAMP) carbon pools in arctic waters, and includes: • to clarify how this carbon is redistrib- • an arctic-optimized SeaMARC™-type uted beneath arctic ice. Sidescan Swath Bathymetric Sonar; The unusual arctic conditions create a • a swept frequency (“chirp”) High situation in which the flux of carbon in Resolution Sub-bottom Profiler; For more information, please contact: its deep basins may be dominated by hori- • a gravimeter; and zontal as much as by vertical processes. • a Data Acquisition and Quality William M. Smethie, Jr. Sampling from the Arctic Ocean Section Control System. ARCUS Representative provided data from the eastern side of the SCAMP was installed and tested on Lamont-Doherty Earth Observatory Canada Basin, while submarine samples the USS Hawkbill during SCICEX ’98. Columbia University provide additional data from these regions, Data were collected along approximately PO Box 1000 as well as parts of the Beaufort Sea and 3,300 km of the Gakkel Ridge. Two 61 Route 9 W. western Canada Basin. Sampling extends segments totaling 250 km were mapped Palisades, NY 10964-8000 into waters of intermediate depth and out to 50 km on either side of the ridge. Phone: 914/365-8566 focuses on the upper halocline that is SCICEX ’99 completed mapping the Fax: 914/365-8155 derived from various inputs, including western portion of the Gakkel Ridge [email protected] river discharge and modified shelf water. and studied the structure of the http://www.ldeo.columbia.edu/ Researchers are trying to identify the Lomonosov Ridge. 4